Python | Check if all elements in list follow a condition

Sometimes, while working with Python list, we can have a problem in which we need to check if all the elements in list abide to a particular condition. This can have application in filtering in web development domain. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using all()
We can use all(), to perform this particular task. In this, we feed the condition and the validation with all the elements is checked by all() internally.

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# Python3 code to demonstrate working of
# Check if all elements in list follow a condition
# Using all()
  
# initializing list
test_list = [4, 5, 8, 9, 10]
  
# printing list
print("The original list : " + str(test_list))
  
# Check if all elements in list follow a condition
# Using all()
res = all(ele > 3 for ele in test_list)
  
# Printing result
print("Are all elements greater than 3 ? : " + str(res))

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Output :

 
The original list : [4, 5, 8, 9, 10]
Are all elements greater than 3 ? : True

 

Method #2 : Using itertools.takewhile()
This function can also be used to code solution of this problem. In this, we just need to process the loop till a condition is met and increment the counter. If it matches list length, then all elements meet that condition.

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# Python3 code to demonstrate working of
# Check if all elements in list follow a condition
# Using itertools.takewhile()
import itertools
  
# initializing list
test_list = [4, 5, 8, 9, 10]
  
# printing list
print("The original list : " + str(test_list))
  
# Check if all elements in list follow a condition
# Using itertools.takewhile()
count = 0
for ele in itertools.takewhile(lambda x: x > 3, test_list):
    count = count + 1
res = count == len(test_list)
  
# Printing result
print("Are all elements greater than 3 ? : " + str(res))

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Output :

 
The original list : [4, 5, 8, 9, 10]
Are all elements greater than 3 ? : True



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